The present invention relates to a method for producing a thin film multilayer substrate or multilayer circuit board which is made by superposing a plurality of conductor pattern layers through dielectric or insulating layers interposed between the conductor pattern layers, and more particularly to a method for producing a thin film multilayer substrate by depositing thin film multilayer conductor patterns on a substrate for mounting LSI chips and the like in an electronic computer or the like.
The present invention relates also to a conductor pattern detecting method which is available for inspection of a configuration of an uppermost conductor pattern of a thin film multilayer conductors superposed alternatingly with dielectric or insulating layers, and it relates to an apparatus therefor.
A technique for using a polyimide resin having a low dielectric constant and a high heat resistance as an insulating layer of a thin film multilayer substrate for mounting LSI chips and the like at a high mounting density is shown in, for example, NEC Technical Report 39, No. 1 (1986), pages 36-41.
Such a technique is also disclosed in NIKKEI MICRODEVICES, January 1988, pages 70 to 77.
However, since this technique is relatively new, only NIKKEI MICRODEVICES, January 1988 shows an outline of a production method, and the prior art fails to show a specific step for inspection of faults of the product during a production process and other steps.
On the other hand, an inspection step of a conductor pattern in a manufacturing process of a thin film multilayer substrate including a semiconductor wafer for LSIs and the like is disclosed in, for example, Japanese Patent Unexamined Publication No. 57-208153. In addition, a technique for inspecting how the pattern has been produced, by using a line width measuring device, is shown in Precision Engineering Association's monthly report 54/4/1988, pages 34 to 38 entitled "TECHNIQUE FOR MEASURING FINE DIMENSION OF WAFER." However, these techniques disclosed in these printed publications are used for checking the manufacturing process of the multilayer substrate and the like and for controlling the condition of the manufacturing process to keep the manufacturing process itself at an optimum condition, by monitoring a pattern formed on a midway of the manufacturing process. The faulty chips and the like which were picked up in the inspection step were finally disposed.
Namely, the above-described prior art inspection methods are available for producing a large amounts of products by using silicon wafers such as LSI chips but are not intended to produce a small amount of products which need a high cost per one product, as in a step for forming a thin film multilayer circuit conductor pattern on a ceramic substrate.
Incidentally, the above-described Japanese Patent Unexamined Publication 57-208153 discloses a method in which, in order to inspect the configuration of a circuit conductor pattern of an uppermost layer of a thin film multilayer circuit conductors superposed alternatingly with insulating films and circuit conductor patterns, a downward or bright field illumination light and a dark field illumination light are simultaneously projected to brightly sense the uppermost layer of circut conductor pattern irrespective of stepped portions and flat portions thereof, whereby an aluminum circuit conductor pattern of the uppermost layers of the multilayer patterns of the LSI wafer is visualized for detection. However, in this case, it is assumed that only one aluminum circuit conductor pattern be formed in the uppermost layer of the multilayer patterns, and the aluminum circuit conductor pattern is visualized due to the fact that the aluminum circuit conductor pattern can be sufficiently brightly sensed in comparison with the lower layers.
On the other hand, the above-described paper entitled "TECHNIQUE FOR MEASURING FINE DIMENSION 0F WAFER" shows a method in which, by utilizing the fact that an organic material such as a resist absorbs ultraviolet rays, the ultraviolet rays are used as illumination light. In this case, the resist pattern which is transparent with the visible light is detected as a dark pattern under the ultraviolet rays with a contrast relative to the other parts.
However, in the prior art, in case of the technique disclosed in Japanese Patent Unexamined publication No. 57-208153, if the aluminum conductor layer is included in the lower layers, the aluminum layer of the lower layers is also brightly sensed, so that it would be impossible to distinguish the uppermost pattern from the lower aluminum conductor pattern. Moreover, in this technique, although the bright field illumination and the dark field illumination light are simultaneously projected, in the case where the stepped portions are provided in the insulating layers and the stepped portions of the insulating layer are inclined in such a angle that a regular reflective light from the stepped portions is received by an optical detector system, the regular refractive light from the insulative film stepped portions would be also detected as a light having a relatively large or substantial instensity. In this case, there is a fear that it would be impossible to detect only the conductor pattern.
On the other hand, in the technique disclosed in the paper entiled "TECHNIQUE FOR MEASURING FINE DIMENSION OF WAFER", there is no consideration of the case where the stepped portions are formed in the circuit conductor pattern. In other words, the light projected on the stepped portions of the circuit conductor pattern is reflected sidewards, as a result of which the stepped portions are detected as dark parts and it would be impossible to distinguish the stepped portions from disconnections of circuit conductors.
Accordingly, the first object of the present invention is to provide a method for enhancing a yield of a thin film multilayer substrate which needs a small-amount production system with a high cost.
An additional object of the invention is to provide a method for enhancing an efficiency of the inspection and the repair of the product.
The second object of the invention is to provide a method and an apparatus for detecting a pattern of an upper most conductor pattern layer of a thin film multilayer substrate relative to stepped portions, lower pattern layers, insulating films and the like.